1. Field of the Invention
The present invention relates to a vehicle-periphery image generating apparatus and a method of correcting distortion of a vehicle-periphery image. In particular, the present invention relates to a vehicle-periphery image generating apparatus for generating a vehicle-periphery image for supporting operation and a method of correcting distortion of an obstacle image appearing in the vehicle-periphery image.
2. Description of the Related Art
Conventionally, there has been proposed a system of generating and displaying a vehicle-periphery image viewed from a virtual point of view above a vehicle by installing a plurality of cameras on the front, rear, left and right sides of the vehicle, and converting images around the vehicle captured by the plurality of cameras, and combining the respective viewpoint-converted images. According to this system, a driver can understand a positional relation between the vehicle and an obstacle near the vehicle by viewing the vehicle-periphery image displayed on a display device, and driving the vehicle so as to prevent collisions.
In such systems, the viewpoint conversion is performed such that the entire object captured by a camera is projected to a height equal to a height of a road surface. Therefore, an image of a three-dimensional obstacle around the vehicle is distorted, particularly toward the far side as viewed from the camera (vehicle), which causes driver visual discomfort. To address the distortion problem, a technique capable of relieving the driver discomfort caused by the distortion is proposed in Japanese Patent Laid-Open Publication No. 2004-213489 (“the JP '489 publication”).
In the technique disclosed in the JP '489 publication, an image of the obstacle shown in the viewpoint-converted image is masked so that only the obstacle's circumferential profile position can be recognized. By using this process, even if a pattern exists in the obstacle, the obstacle is displayed without distortion, and therefore, the uncomfortable sensation due to the distortion can be relieved.
However, in the technique disclosed in the JP '489 publication, the obstacle (e.g., its circumferential profile) in the viewpoint-converted image is shown in a distorted manner. Moreover, only the circumferential profile of the distorted obstacle is displayed. Therefore, it is difficult for a driver to determine what kind of obstacles the displayed profile indicates, which may make a driver uneasy or cause driver discomfort. Further, because the obstacle image around the vehicle is still distorted, it is difficult for a driver to sense the distance between the vehicle and the obstacle.